Humans Stand on Their Own Two Feet 163In fact, the earliest known stone tools, dating to about
2.5 mya, are about 2 million years more recent than the old-
est fossils of Australopithecus. However, Australopithecus
certainly had no less intelligence and dexterity than do
modern great apes, all of whom make use of tools when
it is to their advantage to do so. Orangutans, bonobos,
chimpanzees, and even gorillas have all been observed in
the wild making and using simple tools such as those de-
scribed in Chapter 4. Most likely, the ability to make and
use simple tools is something that goes back to the last
common ancestor of the Asian and African apes, before
the appearance of the first bipeds.
It is reasonable to suppose, then, that australopithecine tool
use was similar to that of the other great apes. Unfortunately,
few tools that they used are likely to have survived for a mil-
lion and more years, and any that did would be hard to rec-
ognize as such. Although we cannot be certain about this, in
addition to clubs and objects thrown for defense, sturdy sticks
may have been used to dig edible roots, and convenient stones
may have been used (as some chimpanzees do) to crack open
nuts. In fact, some animal bones from australopithecine sites
in South Africa show microscopic wear patterns suggesting
their use to dig edible roots from the ground. We may also
allow the possibility that, like chimpanzees, females may have
used tools more often to get and process food than males, but
the latter may have used tools more often as “weapons.”^13 The
female chimpanzees who hunted with spears as described in
Chapter 4 call into question these distinct roles for the sexes.Humans Stand on
Their Own Two Feet
From the broad-shouldered, long-armed, tailless ape body
plan, the human line became fully bipedal. Our late Mio-
cene forebears seem to have been primates that combined
quadrupedal tree climbing with perhaps some swinging
below the branches. On the ground, they were capable of
assuming an upright stance, at least on occasion (optional,
versus obligatory, bipedalism).
Paleoanthropologists generally take the negative as-
pects of bipedal locomotion into account when considering
the advantages of this pattern of locomotion. For exam-
ple, paleoanthropologists have suggested that bipedalism
makes an animal more visible to predators, exposes its
soft underbelly or gut, and interferes with the ability
to instantly change direction while running. They alsotheir hypotheses, paleoanthropologists add to the fossil
evidence through scientific reconstructions of environ-
mental conditions and inferences made from data gathered
on living nonhuman primates and humans. In this regard,
evolutionary reconstructions involve piecing together a co-
herent story or narrative about the past. Sometimes these
narratives are tenuous. But as paleoanthropologists con-
sider their own biases and incorporate new evidence as it is
discovered, the quality of the narrative improves.
For many years, the human evolutionary narrative
has been tied to the emergence of the savannah environ-
ment in eastern Africa as the global climate changes of the
Miocene led to increasingly cooler and dryer conditions.
While the evidence from Ardipithecus shows that the earli-
est members of the human line were forest dwellers, over
time the size of tropical forests decreased or, more com-
monly, broke up into mosaics where patches of forest were
interspersed with savannah or other types of open country.
The forebears of the human line are thought to have lived
in places with access to both trees and open country. With
the breaking up of forests, these early ancestors found
themselves spending more and more time on the ground
and had to adapt to this new, more open environment.
The most obvious problem facing these ancestors in
their new situation, other than getting from one patch of
trees to another, was getting food. As the forest thinned or
shrank, the traditional ape-type foods found in trees be-
came less available, especially in seasons of reduced rainfall.
Therefore, it became more and more necessary to forage on
the ground for foods such as seeds, grasses, and roots. With
reduced canine teeth, early bipeds were relatively defenseless
when down on the ground and were easy targets for numer-
ous carnivorous predators. That predators were a problem is
revealed by the South African fossils, most of which are from
individuals that were dropped into rock fissures by leopards
or, in the case of Dart’s original find, by an eagle.
Many investigators have argued that the hands of early
bipeds took over the weapon functions of the reduced
canine teeth. Hands enabled them to threaten predators by
using wooden objects as clubs and throwing stones. This
quality is shared with many of the other hominoids. Recall
the male chimpanzee (Chapter 4) who wielded objects as
part of his display to obtain alpha status. In australopith-
ecines the use of clubs and throwing stones may have set
the stage for the much later manufacture of more efficient
weapons from bone, wood, and stone.
Although the hands of the later australopithecines
were suitable for tool making, no evidence exists that any
of them actually made stone tools. Similarly, experiments
with captive bonobos have shown that they are capable of
making crude chipped stone tools, but they have never
been known to do so outside of captivity. Thus to be able
to do something is not necessarily equivalent to doing it.
(^13) Goodall, J. (1986). The chimpanzees of Gombe: Patterns of behavior
(pp. 552, 564). Cambridge, MA: Belknap.